Comparing different documents/witnesses in the text-text view

[RobertoRDT]

At the present moment, when switching to the text-text view the available edition levels are automatically displayed in the two text frames, typically diplomatic and interpretative. But if I have multiple texts in my edition, which could be the case for different witnesses of the same work, I am forced to compare diplomatic and interpretative versions of the same witness. It would be quite useful, on the contrary, to compare the diplomatic version of A and of B, or interpretative version of A and of C, etc. In other words, you would be able to compare any edition level of any witness/document, disentangling the text-text view from forcing only one document at a time.

As an alternative, this could go in the collation view (which is the most appropriate place to compare texts), but current development of the integrated edition is occurring for evt-viewer-angular (EVT2+), for EVT2js it doesn't make sense to modify the collation view to this purpose.